This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
The following abbreviations that may be found in the specification and/or the drawing figures are defined as follows:    3GPP third generation partnership project    BB baseband    BW bandwidth    CA carrier aggregation    CC component carrier    CQI channel quality indicator    DL downlink (eNB to UE direction)    DRX discontinuous reception    eNB EUTRAN Node B (evolved Node B/base station)    E-UTRAN evolved UTRAN (LTE)    HARQ hybrid Automatic retransmission request    LTE long term evolution    LTE-A LTE-advanced    MAC medium access control    PCC primary CC    PDCCH physical downlink control channel    PDSCH physical downlink shared channel    PUSCH physical uplink shared channel    RF radio frequency    RRC radio resource control    RSRP reference signal received power    RSRQ reference signal received quality    SCC secondary CC    UE user equipment    UL uplink (UE to eNB direction)    UTRAN universal terrestrial radio access network
In the E-UTRAN system, LTE Release 8 is completed, the LTE Release 9 is being standardized, and the LTE Release 10 is currently under development within the 3GPP. In LTE the downlink access technique is orthogonal frequency multiple division access OFDMA, and the uplink access technique is single carrier, frequency division multiple access SC-FDMA. These access techniques are expected to continue in LTE Release 10.
FIG. 1 shows the overall architecture of the E-UTRAN system. The EUTRAN system includes eNBs, providing the EUTRA user plane and control plane (RRC) protocol terminations towards the UE. The eNBs are interconnected with each other by means of an X2 interface. The eNBs are also connected by means of an S1 interface to an evolved packet core, more specifically to a MME and to a Serving Gateway. The S1 interface supports a many to many relationship between mobility management entities MMEs/Serving Gateways and the eNBs.
In LTE Release 8/9 there are discontinuous reception DRX periods during which a mobile terminal/UE is allowed to power down (sleep or idle mode) to conserve power and the network knows not to send transmissions to it. Other active periods are synchronized to this DRX period. For example FIG. 2 gives a general overview of the DRX concept in E-UTRAN for a single mobile terminal. The PDCCH gives resource allocations to multiple mobile terminals for resources in the UL and DL shared channels, shown as PDSCH and PUSCH. More than one consecutive PDCCH may be used (the duty cycle or ‘on-duration’), but the overall schedule repeats after each DRX.
The UEs synchronize to the PDSCH and aligns to the RRC-Connected/idle mode DRX of the eNB in order to receive possible resource allocations/paging messages from network. One of the parameters needed in RRC-Connected/idle mode terminal is the RRC-Connected/idle mode DRX period so that the UE and eNB have synchronized resource allocation/paging occasions defined by the DRX schedule during which the eNB can send resource allocations or a page to the UE, which tunes to listen at those times.
Though described in view of LTE or E-UTRAN, many current wireless systems use the DRX concept and can benefit from these teachings, as will future systems that employ discontinuous reception at the mobile equipment. For example, the GERAN system uses a paging period (see for example 3GPP TS 45.002) and legacy UTRAN (3G) uses paging and idle mode DRX and continuous packet connectivity (CPC) in the connected mode (see for example 3GPP TS 25.331 and TS 25.304).
LTE-A will likely be part of LTE Release 10 which is to include bandwidth extensions beyond 20 MHz, among other changes. This bandwidth extension is to be done via carrier aggregation (CA), in which several component carriers (at least one of which is Release 8 compatible) are aggregated together to form a system bandwidth. This is shown by example at FIG. 3 in which there are five CCs aggregated to form one larger LTE-A bandwidth of 100 MHz. Future LTE-A terminals could potentially receive/transmit on multiple CCs at the same time to give the eNB greater scheduling flexibility while increasing data throughput.
In LTE-Advanced, multiple DL and/or UL CCs may be configured/activated for one UE. There are two levels of handling CCs: the UE may be configured with basic CC information via RRC signaling, and following configuration the different CCs can be activated and deactivated using MAC level signaling. MAC level signaling (activation and deactivation of CCs) was introduced in order to enable potential UE power savings.
An activated CC is one for which the UE is required to monitor the PDCCH for potential allocations, as well as perform CQI measurements and other procedures set forth in LTE Release 8. The UE does not need to monitor the PDCCH of a deactivated or inactive CC, nor is it required to perform CQI measurements on such a deactivated CC. It follows that in order that the UE to conserve power from having a CC-activation and CC-deactivation command, the UE measurement performance requirements for deactivated CCs has to be different than those that apply for activated CCs. By example, such a CC-activation or deactivation command can be at the MAC level or the RRC level, or possibly at the L1 level in certain embodiments.
As currently set forth at 3GPP TS 36.300 (v9.3.0) sec 12.1 “Carrier Aggregation” (as changed by CR document R2-102645, 3GPP TSG-RAN WG2 Meeting #69, Beijing, China; 12-16 Apr. 2010), if a UE is configured with more than one CC the same DRX operation applies to all configured and activated CCs, so there is identical active time for PDCCH monitoring. The PCC is from a primary cell and is always active; all other configured CCs are termed SCCs which may be from a secondary cell and at any given time any of those SCCs may be active or inactive for the UE for which they are configured. CR document R2-102645 is attached as Appendix A to the priority document U.S. 61/330,621.
A problem arises when the status of a configured CC is changed, for example from deactivated to activated (and also vice versa). The UE needs to tune from the first CC (PCC or some other CC which has remained active) to the newly activated second CC in order to monitor the PDCCH, measure it and report on that second CC. An additional problem occurs when measurements have to be performed on an intra-band deactivated CC (that is, contiguous in frequency with the other CC which remains active) in that still the UE needs to re-tune its radio to the frequency of the other contiguous-band CC. During the time the UE is tuned or needs to re-tune its receiver to receive and measure the other CC, there is a gap during which the UE's DRX pattern for a first CC causes the network to expect that the UE is actively listening to that first CC when in fact the UE is re-tuning in order to measure the other CC.
Embodiments of this invention are directed to how DRX and/or measurement reporting is applied on CC's of a CA system that are actively used by the UE. Currently for LTE-A it is assumed that the DRX cycle will be common to all CCs. At International publication WO/2009/120124, entitled “DRX FUNCTIONALITY IN MULTI-CARRIER WIRELESS NETWORKS”, when there is a gap such as might arise from using a common DRX across multiple CCs, the network sends override commands to disable or to modify the DRX cycles of certain CCs, which this publication appears to characterize as providing independent DRX on the respective CCs.